Swift: How to add more than one item to JSON array? - arrays

Question

I am trying to create a basic to-do application for command-line in Swift. Below is my function to add a new item to the to-do array, but the new entry keeps overwriting the old one, instead of creating a new one. In the end, there is only one entry in the todo.json file.
When I multiply the entries and .append statements manually it works, but probably my brain is too dead to figure it out at the moment.
struct TodoItem: Codable {
let name: String
}
var todoList = [TodoItem]()
func addToList(_ item: String) -> String {
let todoItem = TodoItem(name: item)
todoList.append(todoItem)
do {
let fileURL = try FileManager.default
.url(for: .applicationSupportDirectory,
in: .userDomainMask,
appropriateFor: nil,
create: true)
.appendingPathComponent("example")
.appendingPathExtension("json")
let encoder = JSONEncoder()
try encoder.encode(todoList).write(to: fileURL)
} catch {
return "Error: \(error.localizedDescription)"
}
return "Item added: \(todoItem.name)"
}

Answer 1

Your code works fine. I think the problem rests in the fact that todoList is empty when you run this. But you can write code to retrieve the contents of the JSON:
var todoList: [TodoItem] = []
func retrieveToDoList() {
guard let data = try? Data(contentsOf: fileURL) else { return }
todoList = (try? JSONDecoder().decode([TodoItem].self, from: data)) ?? []
}
So, for example, consider:
retrieveToDoList()
addToList("foo")
addToList("bar")
addToList("baz")
print(todoList)
// if you want to check the json
let data = try! Data(contentsOf: fileURL)
let json = String(data: data, encoding: .utf8)!
print(json)
That results in:
[MyApp.TodoItem(name: "foo"), MyApp.TodoItem(name: "bar"), MyApp.TodoItem(name: "baz")]
[
{
"name" : "foo"
},
{
"name" : "bar"
},
{
"name" : "baz"
}
]
And if I later do:
addToList("abc")
addToList("def")
addToList("hij")
I then get:
[
{
"name" : "foo"
},
{
"name" : "bar"
},
{
"name" : "baz"
},
{
"name" : "abc"
},
{
"name" : "def"
},
{
"name" : "hij"
}
]
So, every time the app starts up, just make sure to call retrieveToDoList before trying to append items or else the toDoList will be empty.
FYI, this is the code I used to generate the above. Hopefully it illustrates the idea.
struct TodoItem: Codable {
let name: String
}
class ViewController: UIViewController {
private var todoList: [TodoItem] = []
private let fileURL = try! FileManager.default
.url(for: .applicationSupportDirectory,
in: .userDomainMask,
appropriateFor: nil,
create: true)
.appendingPathComponent("example.json")
override func viewDidLoad() {
super.viewDidLoad()
retrieveToDoList()
addToList("foo")
addToList("bar")
addToList("baz")
print(todoList)
// if you want to check the json
let data = try! Data(contentsOf: fileURL)
let json = String(data: data, encoding: .utf8)!
print(json)
}
}
private extension ViewController {
func retrieveToDoList() {
guard let data = try? Data(contentsOf: fileURL) else { return }
todoList = (try? JSONDecoder().decode([TodoItem].self, from: data)) ?? []
}
#discardableResult
func addToList(_ item: String) -> String {
let todoItem = TodoItem(name: item)
todoList.append(todoItem)
do {
let encoder = JSONEncoder()
encoder.outputFormatting = .prettyPrinted
try encoder.encode(todoList).write(to: fileURL)
} catch {
return "Error: \(error.localizedDescription)"
}
return "Item added: \(todoItem.name)"
}
}